The introduction of copper (Cu) metal into multilayer metallization schemes for manufacturing integrated circuits, can require the use diffusion barriers/liners to promote adhesion and growth of the Cu layers, and to chemically isolate the Cu from the dielectric material to prevent diffusion of Cu into the dielectric material.
Barriers/liners that are deposited onto dielectric materials can include refractive materials such as tungsten (W), molybdenum (Mo), and tantalum (Ta), that are non-reactive and immiscible with Cu and can offer low electrical resistivity. Basic material properties of W, such as electrical resistivity, thermal stability, and diffusion barrier properties make W layers suitable for use in advanced Cu-based interconnect applications. Current integration schemes that integrate Cu metallization and dielectric materials can require W barrier/liner deposition processes at substrate temperatures between about 400° C. and about 500° C., or lower.
W layers can be formed on a substrate in a thermal chemical vapor deposition (TCVD) process by thermally decomposing a tungsten-halide precursor, e.g., tungsten hexafluoride (WF6), in the presence of a reducing gas such as hydrogen or silane. A drawback to using tungsten-halide precursors is incorporation of halide by-products in the W layer that can degrade the material properties of the W layer. A non-halogen containing tungsten precursor, such as a tungsten-carbonyl precursor, can be used to alleviate the abovementioned drawbacks associated with tungsten-halide precursors. However, material properties of W layers that are formed by thermal decomposition of tungsten-carbonyl precursors (e.g., W(CO)6), can deteriorate due to incorporation of CO reaction by-products into the thermally deposited W layers, resulting in increase in the electrical resistivity of the W layers and formation of W layers with poor conformality.